Integrated Illumination And Detection For LIDAR Based 3-D Imaging

ABSTRACT

Methods and systems for performing three dimensional LIDAR measurements with a highly integrated LIDAR measurement device are described herein. In one aspect, the illumination source, detector, and illumination drive are integrated onto a single printed circuit board. In addition, in some embodiments, the associated control and signal conditioning electronics are also integrated onto the common printed circuit board. Furthermore, in some embodiments, the illumination drive and the illumination source are integrated onto a common Gallium Nitride substrate that is independently packaged and attached to the printed circuit board. In another aspect, the illumination light emitted from the illumination source and the return light directed toward the detector share a common optical path within the integrated LIDAR measurement device. In some embodiments, the return light is separated from the illumination light by a beam splitter. In some other embodiments, the optical design avoids losses associated with a beam splitter.

CROSS REFERENCE TO RELATED APPLICATION

The present application for patent claims priority under 35 U.S.C. §119from U.S. provisional patent application Ser. No. 62/310,670, entitled“Integrated Illumination and Detection for LIDAR Based 3-D Imaging,”filed Mar. 19, 2016, the subject matter of which is incorporated hereinby reference in its entirety.

TECHNICAL FIELD

The described embodiments relate to LIDAR based 3-D point cloudmeasuring systems.

BACKGROUND INFORMATION

LIDAR systems employ pulses of light to measure distance to an objectbased on the time of flight (TOF) of each pulse of light. A pulse oflight emitted from a light source of a LIDAR system interacts with adistal object. A portion of the light reflects from the object andreturns to a detector of the LIDAR system. Based on the time elapsedbetween emission of the pulse of light and detection of the returnedpulse of light, a distance is estimated. In some examples, pulses oflight are generated by a laser emitter. The light pulses are focusedthrough a lens or lens assembly. The time it takes for a pulse of laserlight to return to a detector mounted near the emitter is measured. Adistance is derived from the time measurement with high accuracy.

Some LIDAR systems employ a single laser emitter/detector combinationcombined with a rotating mirror to effectively scan across a plane.Distance measurements performed by such a system are effectively twodimensional (i.e., planar), and the captured distance points arerendered as a 2-D (i.e. single plane) point cloud. In some examples,rotating mirrors are rotated at very fast speeds (e.g., thousands ofrevolutions per minute).

In many operational scenarios, a 3-D point cloud is required. A numberof schemes have been employed to interrogate the surrounding environmentin three dimensions. In some examples, a 2-D instrument is actuated upand down and/or back and forth, often on a gimbal. This is commonlyknown within the art as “winking” or “nodding” the sensor. Thus, asingle beam LIDAR unit can be employed to capture an entire 3-D array ofdistance points, albeit one point at a time. In a related example, aprism is employed to “divide” the laser pulse into multiple layers, eachhaving a slightly different vertical angle. This simulates the noddingeffect described above, but without actuation of the sensor itself.

In all the above examples, the light path of a single laseremitter/detector combination is somehow altered to achieve a broaderfield of view than a single sensor. The number of pixels such devicescan generate per unit time is inherently limited due limitations on thepulse repetition rate of a single laser. Any alteration of the beampath, whether it is by mirror, prism, or actuation of the device thatachieves a larger coverage area comes at a cost of decreased point clouddensity.

As noted above, 3-D point cloud systems exist in several configurations.However, in many applications it is necessary to see over a broad fieldof view. For example, in an autonomous vehicle application, the verticalfield of view should extend down as close as possible to see the groundin front of the vehicle. In addition, the vertical field of view shouldextend above the horizon, in the event the car enters a dip in the road.In addition, it is necessary to have a minimum of delay between theactions happening in the real world and the imaging of those actions. Insome examples, it is desirable to provide a complete image update atleast five times per second. To address these requirements, a 3-D LIDARsystem has been developed that includes an array of multiple laseremitters and detectors. This system is described in U.S. Pat. No.7,969,558 issued on Jun. 28, 2011, the subject matter of which isincorporated herein by reference in its entirety.

In many applications, a sequence of pulses is emitted. The direction ofeach pulse is sequentially varied in rapid succession. In theseexamples, a distance measurement associated with each individual pulsecan be considered a pixel, and a collection of pixels emitted andcaptured in rapid succession (i.e., “point cloud”) can be rendered as animage or analyzed for other reasons (e.g., detecting obstacles). In someexamples, viewing software is employed to render the resulting pointclouds as images that appear three dimensional to a user. Differentschemes can be used to depict the distance measurements as 3-D imagesthat appear as if they were captured by a live action camera.

Some existing LIDAR systems employ an illumination source and a detectorthat are not integrated together onto a common substrate (e.g.,electrical mounting board). Furthermore, the illumination beam path andthe collection beam path are separated within the LIDAR device. Thisleads to opto-mechanical design complexity and alignment difficulty.

Improvements in the opto-mechanical design of LIDAR systems are desired,while maintaining high levels of imaging resolution and range.

SUMMARY

Methods and systems for performing three dimensional LIDAR measurementswith a highly integrated LIDAR measurement device are described herein.In one aspect, the illumination source, detector, and illumination driveare integrated onto a single printed circuit board. In addition, in someembodiments, the associated control and signal conditioning electronicsare also integrated onto the common printed circuit board. Furthermore,in some embodiments, the illumination drive and the illumination sourceare integrated onto a common Gallium Nitride substrate that isindependently packaged and attached to the printed circuit board.

In some embodiments a 3-D LIDAR system includes multiple integratedLIDAR measurement devices. In some embodiments, a delay time is setbetween the firing of each integrated LIDAR measurement device. In someexamples, the delay time is greater than the time of flight of themeasurement pulse sequence to and from an object located at the maximumrange of the LIDAR device. In this manner, there is no cross-talk amongany of the integrated LIDAR measurement devices. In some other examples,a measurement pulse is emitted from one integrated LIDAR measurementdevice before a measurement pulse emitted from another integrated LIDARmeasurement device has had time to return to the LIDAR device. In theseembodiments, care is taken to ensure that there is sufficient spatialseparation between the areas of the surrounding environment interrogatedby each beam to avoid cross-talk.

In another aspect, the illumination light emitted from the illuminationsource and the return light directed toward the detector share a commonoptical path within the integrated LIDAR measurement device. In someembodiments, the return light is separated from the illumination lightby a beam splitter. In general, when the polarization of the returnlight is completely mixed and a single polarizing beam splitter isemployed, half of the return light will be directed toward detector andthe other half will be directed toward the illumination source. In someother embodiments, these losses are avoided by employing one or morepolarization control elements to alter the polarization state of lightpassing through the polarization control element in coordination withthe firing of the illumination source and the timing of the measurementtime window to minimize losses of return light.

In some other embodiments, the return light is separated from theillumination light by optical design to avoid losses associated with abeam splitter.

In some embodiments, a detector includes a slot through the detectorincluding the active sensing area. The illumination source is fixed tothe back of the detector and is configured to emit illumination lightthrough the slot in the detector. In this manner, both the detector andillumination source are located in the beam path of light emitted froman integrated LIDAR measurement device and returned to the integratedLIDAR measurement device. Although a certain amount of return light willbe directed toward the slot and not detected, the relatively small areaof the slot compared to the active area of the detector ensures that themajority of the return light is detected.

In some embodiments, the illumination source is located outside thefield of view of the detector. In some embodiments, the index ofrefraction of an active optical element is controlled to pass returnlight and refract illumination light toward the common optical pathshared by both the illumination light and the return light. Theillumination light is not initially aligned with the optical axis of theoptical system. However, during periods of time when light is emittedfrom the illumination source, the active optical element changes itsstate such that the illumination light is aligned with the optical axisof the optical system.

In some embodiments, a concentric focusing optic focuses return lightonto the detector and a passive optical element located in the middle ofthe concentric focusing optic refracts the illumination light toward thecommon optical path shared by both the illumination light and the returnlight.

In some embodiments, the return light reflects from a mirror element andpropagates toward the detector. In one aspect, the mirror includes aslot through which the illumination light is passed. This effectivelyinjects the illumination light into the common optical path shared by byboth the illumination light and the return light.

In some embodiments, the illumination source is located in the opticalpath of the return light in front of the detector.

In some other embodiments, the illumination source is embedded in anoptical element that is located in the optical path of the return lightin front of the detector.

In another aspect, illumination light is injected into the detectorreception cone by a waveguide. An optical coupler optically couples andillumination source to the waveguide. At the end of the waveguide, amirror element is oriented at a 45 degree angle with respect to thewaveguide to inject the illumination light into the cone of returnlight. In some embodiments, the waveguide includes a rectangular shapedglass core and a polymer cladding of lower index of refraction. In someembodiments, the entire assembly is encapsulated with a material havingan index of refraction that closely matches the index of refraction ofthe polymer cladding. In this manner, the waveguide injects theillumination light into the acceptance cone of return light with minimalocclusion.

In some embodiments, an array of integrated LIDAR measurement devices ismounted to a rotating frame of the LIDAR device. This rotating framerotates with respect to a base frame of the LIDAR device. However, ingeneral, an array of integrated LIDAR measurement devices may be movablein any suitable manner (e.g., gimbal, pan/tilt, etc.) or fixed withrespect to a base frame of the LIDAR device.

In some other embodiments, each integrated LIDAR measurement deviceincludes a beam directing element (e.g., a scanning mirror, MEMS mirroretc.) that scans the illumination beam generated by the integrated LIDARmeasurement device.

In some other embodiments, two or more integrated LIDAR measurementdevices each emit a beam of illumination light toward a scanning mirrordevice (e.g., MEMS mirror) that reflects the beams into the surroundingenvironment in different directions.

The foregoing is a summary and thus contains, by necessity,simplifications, generalizations and omissions of detail; consequently,those skilled in the art will appreciate that the summary isillustrative only and is not limiting in any way. Other aspects,inventive features, and advantages of the devices and/or processesdescribed herein will become apparent in the non-limiting detaileddescription set forth herein.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a simplified diagram illustrative of one embodiment of a 3-DLIDAR system 100 in at least one novel aspect.

FIG. 2 is a simplified diagram illustrative of another embodiment of a3-D LIDAR system 10 in at least one novel aspect.

FIG. 3 depicts an exploded view of 3-D LIDAR system 100 in one exemplaryembodiment.

FIG. 4 depicts a view of collection optics 116 of 3-D LIDAR system 100in greater detail.

FIG. 5 depicts a cutaway view of collection optics 116 of 3-D LIDARsystem 100 that illustrates the shaping of each beam of collected light118.

FIG. 6 is a simplified diagram illustrative of an integrated LIDARmeasurement device in one embodiment.

FIG. 7 is a simplified schematic diagram illustrative of an integratedLIDAR measurement device in another embodiment.

FIG. 8 depicts an illustration of the timing associated with theemission of a measurement pulse from an integrated LIDAR measurementdevice and capture of the returning measurement pulse.

FIG. 9 depicts a front view of an embodiment of an integrated LIDARmeasurement device including a detector having a slot through whichillumination light is projected from an illumination source.

FIG. 10 depicts a side view of the embodiment depicted in FIG. 9.

FIG. 11 depicts a side view of an embodiment of an integrated LIDARmeasurement device including an active optical element in one state thatcauses illumination light to refract toward a shared optical path.

FIG. 12 depicts a side view of the embodiment depicted in FIG. 11including the active optical element in another state that causes returnlight to be directed toward a detector.

FIG. 13 depicts a side view of an embodiment of an integrated LIDARmeasurement device including a concentric focusing optic to focus returnlight onto a detector and another optical element that causesillumination light to refract toward a shared optical path.

FIG. 14 depicts a top view of an embodiment of an integrated LIDARmeasurement device including a mirror in the return path having a slotthrough which illumination light is passed.

FIGS. 15A-C depict three different light paths through an embodiment ofan integrated LIDAR measurement device employing a polarization controlelement.

FIG. 16 depicts an embodiment of an integrated LIDAR measurement devicethat includes an additional polarization control element to effectivelycontrol the amount of return light that reaches a detector.

FIG. 17 depicts an embodiment of an integrated LIDAR measurement devicethat includes additional, optional elements that may be addedindividually, or in any combination, to the embodiment described withreference to FIGS. 15A-C.

FIG. 18 depicts a side view of an embodiment of an integrated LIDARmeasurement device including an illumination source in a common opticalpath in front of the detector.

FIG. 19 depicts a front view of the embodiment depicted in FIG. 18.

FIG. 20 depicts a side view of an embodiment of an integrated LIDARmeasurement device including an illumination source embedded in anoptical element in a common optical path in front of the detector.

FIG. 21 depicts a side view of an embodiment of an integrated LIDARmeasurement device including a waveguide that injects illumination lightinto a common optical path shared by the illumination light and thereturn light.

FIG. 22 depicts a flowchart illustrative of a method 300 of performingLIDAR measurements in at least one novel aspect.

DETAILED DESCRIPTION

Reference will now be made in detail to background examples and someembodiments of the invention, examples of which are illustrated in theaccompanying drawings.

FIG. 1 is a diagram illustrative of an embodiment of a 3-D LIDAR system100 in one exemplary operational scenario. 3-D LIDAR system 100 includesa lower housing 101 and an upper housing 102 that includes a domed shellelement 103 constructed from a material that is transparent to infraredlight (e.g., light having a wavelength within the spectral range of 700to 1,700 nanometers). In one example, domed shell element 103 istransparent to light having a wavelengths centered at 905 nanometers.

As depicted in FIG. 1, a plurality of beams of light 105 are emittedfrom 3-D LIDAR system 100 through domed shell element 103 over anangular range, a, measured from a central axis 104. In the embodimentdepicted in FIG. 1, each beam of light is projected onto a plane definedby the x and y axes at a plurality of different locations spaced apartfrom one another. For example, beam 106 is projected onto the xy planeat location 107.

In the embodiment depicted in FIG. 1, 3-D LIDAR system 100 is configuredto scan each of the plurality of beams of light 105 about central axis104. Each beam of light projected onto the xy plane traces a circularpattern centered about the intersection point of the central axis 104and the xy plane. For example, over time, beam 106 projected onto the xyplane traces out a circular trajectory 108 centered about central axis104.

FIG. 2 is a diagram illustrative of another embodiment of a 3-D LIDARsystem 10 in one exemplary operational scenario. 3-D LIDAR system 10includes a lower housing 11 and an upper housing 12 that includes acylindrical shell element 13 constructed from a material that istransparent to infrared light (e.g., light having a wavelength withinthe spectral range of 700 to 1,700 nanometers). In one example,cylindrical shell element 13 is transparent to light having awavelengths centered at 905 nanometers.

As depicted in FIG. 2, a plurality of beams of light 15 are emitted from3-D LIDAR system 10 through cylindrical shell element 13 over an angularrange, β. In the embodiment depicted in FIG. 2, the chief ray of eachbeam of light is illustrated. Each beam of light is projected outwardinto the surrounding environment in a plurality of different directions.For example, beam 16 is projected onto location 17 in the surroundingenvironment. In some embodiments, each beam of light emitted from system10 diverges slightly. In one example, a beam of light emitted fromsystem 10 illuminates a spot size of 20 centimeters in diameter at adistance of 100 meters from system 10. In this manner, each beam ofillumination light is a cone of illumination light emitted from system10.

In the embodiment depicted in FIG. 2, 3-D LIDAR system 10 is configuredto scan each of the plurality of beams of light 15 about central axis14. For purposes of illustration, beams of light 15 are illustrated inone angular orientation relative to a non-rotating coordinate frame of3-D LIDAR system 10 and beams of light 15′ are illustrated in anotherangular orientation relative to the non-rotating coordinate frame. Asthe beams of light 15 rotate about central axis 14, each beam of lightprojected into the surrounding environment (e.g., each cone ofillumination light associated with each beam) illuminates a volume ofthe environment corresponding the cone shaped illumination beam as it isswept around central axis 14.

FIG. 3 depicts an exploded view of 3-D LIDAR system 100 in one exemplaryembodiment. 3-D LIDAR system 100 further includes a lightemission/collection engine 112 that rotates about central axis 104. Inthe embodiment depicted in FIG. 3, a central optical axis 117 of lightemission/collection engine 112 is tilted at an angle, θ, with respect tocentral axis 104. As depicted in FIG. 3, 3-D LIDAR system 100 includes astationary electronics board 110 mounted in a fixed position withrespect to lower housing 101. Rotating electronics board 111 is disposedabove stationary electronics board 110 and is configured to rotate withrespect to stationary electronics board 110 at a predeterminedrotational velocity (e.g., more than 200 revolutions per minute).Electrical power signals and electronic signals are communicated betweenstationary electronics board 110 and rotating electronics board 111 overone or more transformer, capacitive, or optical elements, resulting in acontactless transmission of these signals. Light emission/collectionengine 112 is fixedly positioned with respect to the rotatingelectronics board 111, and thus rotates about central axis 104 at thepredetermined angular velocity, w.

As depicted in FIG. 3, light emission/collection engine 112 includes anarray of integrated LIDAR measurement devices 113. In one aspect, eachintegrated LIDAR measurement device includes a light emitting element, alight detecting element, and associated control and signal conditioningelectronics integrated onto a common substrate (e.g., printed circuitboard or other electrical circuit board).

Light emitted from each integrated LIDAR measurement device passesthrough a series of optical elements 116 that collimate the emittedlight to generate a beam of illumination light projected from the 3-DLIDAR system into the environment. In this manner, an array of beams oflight 105, each emitted from a different LIDAR measurement device areemitted from 3-D LIDAR system 100 as depicted in FIG. 1. In general, anynumber of LIDAR measurement devices can be arranged to simultaneouslyemit any number of light beams from 3-D LIDAR system 100. Lightreflected from an object in the environment due to its illumination by aparticular LIDAR measurement device is collected by optical elements116. The collected light passes through optical elements 116 where it isfocused onto the detecting element of the same, particular LIDARmeasurement device. In this manner, collected light associated with theillumination of different portions of the environment by illuminationgenerated by different LIDAR measurement devices is separately focusedonto the detector of each corresponding LIDAR measurement device.

FIG. 4 depicts a view of optical elements 116 in greater detail. Asdepicted in FIG. 4, optical elements 116 include four lens elements116A-D arranged to focus collected light 118 onto each detector of thearray of integrated LIDAR measurement devices 113. In the embodimentdepicted in FIG. 4, light passing through optics 116 is reflected frommirror 124 and is directed onto each detector of the array of integratedLIDAR measurement devices 113. In some embodiments, one or more of theoptical elements 116 is constructed from one or more materials thatabsorb light outside of a predetermined wavelength range. Thepredetermined wavelength range includes the wavelengths of light emittedby the array of integrated LIDAR measurement devices 113. In oneexample, one or more of the lens elements are constructed from a plasticmaterial that includes a colorant additive to absorb light havingwavelengths less than infrared light generated by each of the array ofintegrated LIDAR measurement devices 113. In one example, the colorantis Epolight 7276A available from Aako BV (The Netherlands). In general,any number of different colorants can be added to any of the plasticlens elements of optics 116 to filter out undesired spectra.

FIG. 5 depicts a cutaway view of optics 116 to illustrate the shaping ofeach beam of collected light 118.

A LIDAR system, such as 3-D LIDAR system 10 depicted in FIG. 2, andsystem 100, depicted in FIG. 1, includes a plurality of integrated LIDARmeasurement devices each emitting a pulsed beam of illumination lightfrom the LIDAR device into the surrounding environment and measuringreturn light reflected from objects in the surrounding environment.

FIG. 6 depicts an integrated LIDAR measurement device 120 in oneembodiment. Integrated LIDAR measurement device 120 includes a pulsedlight emitting device 122, a light detecting element 123, associatedcontrol and signal conditioning electronics integrated onto a commonsubstrate 121 (e.g., electrical board), and connector 126. Pulsedemitting device 122 generates pulses of illumination light 124 anddetector 123 detects collected light 125. Integrated LIDAR measurementdevice 120 generates digital signals indicative of the distance betweenthe 3-D LIDAR system and an object in the surrounding environment basedon a time of flight of light emitted from the integrated LIDARmeasurement device 120 and detected by the integrated LIDAR measurementdevice 120. Integrated LIDAR measurement device 120 is electricallycoupled to the 3-D LIDAR system via connector 126. Integrated LIDARmeasurement device 120 receives control signals from the 3-D LIDARsystem and communicates measurement results to the 3-D LIDAR system overconnector 126.

FIG. 7 depicts a schematic view of an integrated LIDAR measurementdevice 130 in another embodiment. Integrated LIDAR measurement device130 includes a pulsed light emitting device 134, a light detectingelement 138, a beam splitter 135 (e.g., polarizing beam splitter,non-polarizing beam splitter, dielectric film, etc.), an illuminationdriver 133, signal conditioning electronics 139, analog to digital (A/D)conversion electronics 140, controller 132, and digital input/output(I/O) electronics 131 integrated onto a common substrate 144. In someembodiments, these elements are individually mounted to a commonsubstrate (e.g., printed circuit board). In some embodiments, groups ofthese elements are packaged together and the integrated package ismounted to a common substrate. In general, each of the elements aremounted to a common substrate to create an integrated device, whetherthey are individually mounted or mounted as part of an integratedpackage.

FIG. 8 depicts an illustration of the timing associated with theemission of a measurement pulse from an integrated LIDAR measurementdevice 130 and capture of the returning measurement pulse. As depictedin FIGS. 7 and 8, the measurement begins with a pulse firing signal 146generated by controller 132. Due to internal system delay, a pulse indexsignal 149 is determined by controller 132 that is shifted from thepulse firing signal 146 by a time delay, T_(D). The time delay includesthe known delays associated with emitting light from the LIDAR system(e.g., signal communication delays and latency associated with theswitching elements, energy storage elements, and pulsed light emittingdevice) and known delays associated with collecting light and generatingsignals indicative of the collected light (e.g., amplifier latency,analog-digital conversion delay, etc.).

As depicted in FIGS. 7 and 8, a return signal 147 is detected by theLIDAR system in response to the illumination of a particular location. Ameasurement window (i.e., a period of time over which collected returnsignal data is associated with a particular measurement pulse) isinitiated by enabling data acquisition from detector 138. Controller 132controls the timing of the measurement window to correspond with thewindow of time when a return signal is expected in response to theemission of a measurement pulse sequence. In some examples, themeasurement window is enabled at the point in time when the measurementpulse sequence is emitted and is disabled at a time corresponding to thetime of flight of light over a distance that is substantially twice therange of the LIDAR system. In this manner, the measurement window isopen to collect return light from objects adjacent to the LIDAR system(i.e., negligible time of flight) to objects that are located at themaximum range of the LIDAR system. In this manner, all other light thatcannot possibly contribute to useful return signal is rejected.

As depicted in FIG. 8, return signal 147 includes two return measurementpulses that correspond with the emitted measurement pulse. In general,signal detection is performed on all detected measurement pulses.Further signal analysis may be performed to identify the closest signal(i.e., first instance of the return measurement pulse), the strongestsignal, and the furthest signal (i.e., last instance of the returnmeasurement pulse in the measurement window). Any of these instances maybe reported as potentially valid distance measurements by the LIDARsystem. For example, a time of flight, TOF₁, may be calculated from theclosest (i.e., earliest) return measurement pulse that corresponds withthe emitted measurement pulse as depicted in FIG. 8.

In some embodiments, the signal analysis is performed by controller 132,entirely. In these embodiments, signals 143 communicated from integratedLIDAR measurement device 130 include an indication of the distancesdetermined by controller 132. In some embodiments, signals 143 includethe digital signals 148 generated by A/D converter 140. These rawmeasurement signals are processed further by one or more processorslocated on board the 3-D LIDAR system, or external to the 3-D LIDARsystem to arrive at a measurement of distance. In some embodiments,controller 132 performs preliminary signal processing steps on signals148 and signals 143 include processed data that is further processed byone or more processors located on board the 3-D LIDAR system, orexternal to the 3-D LIDAR system to arrive at a measurement of distance.

In some embodiments a 3-D LIDAR system includes multiple integratedLIDAR measurement devices, such as the LIDAR systems illustrated inFIGS. 1-3. In some embodiments, a delay time is set between the firingof each integrated LIDAR measurement device. Signal 142 includes anindication of the delay time associated with the firing of integratedLIDAR measurement device 130. In some examples, the delay time isgreater than the time of flight of the measurement pulse sequence to andfrom an object located at the maximum range of the LIDAR device. In thismanner, there is no cross-talk among any of the integrated LIDARmeasurement devices. In some other examples, a measurement pulse isemitted from one integrated LIDAR measurement device before ameasurement pulse emitted from another integrated LIDAR measurementdevice has had time to return to the LIDAR device. In these embodiments,care is taken to ensure that there is sufficient spatial separationbetween the areas of the surrounding environment interrogated by eachbeam to avoid cross-talk.

Illumination driver 133 generates a pulse electrical current signal 145in response to pulse firing signal 146. Pulsed light emitting device 134generates pulsed light emission 136 in response to pulsed electricalcurrent signal 145. The illumination light 136 is focused and projectedonto a particular location in the surrounding environment by one or moreoptical elements of the LIDAR system (not shown).

In some embodiments, the pulsed light emitting device is laser based(e.g., laser diode). In some embodiments, the pulsed illuminationsources are based on one or more light emitting diodes. In general, anysuitable pulsed illumination source may be contemplated.

In some embodiments, digital I/O 131, timing logic 132, A/D conversionelectronics 140, and signal conditioning electronics 139 are integratedonto a single, silicon-based microelectronic chip. In anotherembodiment, these same elements are integrated into a singlegallium-nitride or silicon based circuit that also includes theillumination driver. In some embodiments, the A/D conversion electronicsand controller 132 are combined as a time-to-digital converter.

As depicted in FIG. 7, return light 137 reflected from the surroundingenvironment is detected by light detector 138. In some embodiments,light detector 138 is an avalanche photodiode. Light detector 138generates an output signal 147 that is amplified by signal conditioningelectronics 139. In some embodiments, signal conditioning electronics139 includes an analog trans-impedance amplifier. However, in general,the amplification of output signal 147 may include multiple, amplifierstages. In this sense, an analog trans-impedance amplifier is providedby way of non-limiting example, as many other analog signalamplification schemes may be contemplated within the scope of thispatent document.

The amplified signal is communicated to A/D converter 140. The digitalsignals are communicated to controller 132. Controller 132 generates anenable/disable signal employed to control the timing of data acquisitionby ADC 140 in concert with pulse firing signal 146.

As depicted in FIG. 7, the illumination light 136 emitted fromintegrated LIDAR measurement device 130 and the return light 137directed toward integrated LIDAR measurement device share a common path.In the embodiment depicted in FIG. 7, the return light 137 is separatedfrom the illumination light 136 by a polarizing beam splitter (PBS) 135.PBS 135 could also be a non-polarizing beam splitter, but this generallywould result in an additional loss of light. In this embodiment, thelight emitted from pulsed light emitting device 134 is polarized suchthat the illumination light passes through PBS 135. However, returnlight 137 generally includes a mix of polarizations. Thus, PBS 135directs a portion of the return light toward detector 138 and a portionof the return light toward pulsed light emitting device 134. In someembodiments, it is desirable to include a quarter waveplate after PBS135. This is advantageous in situations when the polarization of thereturn light is not significantly changed by its interaction with theenvironment. Without the quarter waveplate, the majority of the returnlight would pass through PBS 135 and be directed toward the pulsed lightemitting device 134, which is undesireable. However, with the quarterwaveplate, the majority of the return light will pass through PBS 135and be directed toward detector 138.

However, in general, when the polarization of the return light iscompletely mixed and a single PBS is employed as depicted in FIG. 7,half of the return light will be directed toward detector 138, and theother half will be directed toward pulse light emitting device 134,regardless of whether a quarter waveplate is used.

FIGS. 9-17 depict various embodiments to avoid these losses.

FIG. 9 depicts a front view of an embodiment 150 of an integrated LIDARmeasurement device including a detector 151 (e.g., an avalanchephotodiode) having a circular shaped active area 152 with a diameter, D.In one example, the diameter of the active area 152 is approximately 300micrometers. In one aspect, detector 151 includes a slot 153 all the waythrough the detector. In one example, the slot has a height, H_(S), ofapproximately 70 micrometers and a width, W, of approximately 200micrometers.

FIG. 10 depicts a side view of embodiment 150 depicted in FIG. 9. Asdepicted in FIG. 10, embodiment 150 also includes pulsed light emittingdevice 153 fixed to the back of avalanche photodiode detector 151 andconfigured to emit illumination light 154 through slot 153 in detector151. In one example, pulse light emitting device 153 include three laserdiodes packaged together to create an emission area having a height,H_(E), of 10 micrometers with a divergence angle of approximately 15degrees. In this example, the thickness, S, of the detector 151 isapproximately 120 micrometers.

In this manner, detector 151 and pulsed light emitting device 153 arelocated in the beam path of light emitted from an integrated LIDARmeasurement device and returned to the integrated LIDAR measurementdevice. Although a certain amount of return light will be directedtoward slot 153 and not detected, the relatively small area of slot 153compared to the active area 152 of detector 151 ensures that themajority of the return light will be detected.

FIG. 11 depicts a side view of an embodiment 160 of an integrated LIDARmeasurement device including a detector 162 having an active area 163, apulsed light emitting device 161 located outside of the active area 163,a focusing optic 164 and an active optical element 165. Active opticalelement 165 is coupled to a controller of the integrated LIDARmeasurement device. The controller communicates control signal 167 toactive element 165 that causes the active optical element to changestates.

In a first state, depicted in FIG. 11, the active optical elementchanges its effective index of refraction and causes the light 166emitted from pulsed light emitting device 161 to refract toward opticalaxis, OA.

In a second state, depicted in FIG. 12, the active optical elementchanges its effective index of refraction such that return light 168passes through active optical element 165 and focusing optic 164 towardthe active area 163 of detector 162. During this state, the controllercontrols pulsed light emitting device 161 such that it does not emitlight.

In this embodiment, the light emitted by pulsed light emitting device161 is not initially aligned with the optical axis of the opticalsystem. However, during periods of time when light is emitted from thepulsed light emitting device 161, active optical element changes itsstate such that the illumination light is aligned with the optical axisof the optical system. In some embodiments, the active optical elementis a phase array. In some embodiments, the active optical element is aacousto-optical modulator. In some embodiments, the active opticalelement is a surface acoustic wave modulator. In general, many activedevices capable of altering their effective index of refraction may becontemplated.

FIG. 13 depicts a side view of an embodiment 170 of an integrated LIDARmeasurement device including a detector 173 having an active area 172, apulsed light emitting device 171 located outside of the active area 172,concentric focusing optics 174 and focusing optics 175 centered alongthe optical axis of the integrated LIDAR measurement device. As depictedin FIG. 13, the return light 177 is focused onto the active area 172 ofdetector 173 by concentric focusing optics 174. In addition, light 176emitted from pulsed light emitting device 171 is refracted towardoptical axis, OA, and collimated by focusing optics 175. As depicted inFIG. 13, focusing optics 175 occupy a relatively small area immediatelycentered about the optical axis. Concentric focusing optics are alsocentered about the optical axis, but are spaced apart from the opticalaxis.

FIG. 14 depicts a top view of an embodiment 180 of an integrated LIDARmeasurement device including a detector 187 having an active area 183, apulsed light emitting device 181 located outside of the active area 183,concentric focusing optics 184, and mirror 182. As depicted in FIG. 14,return light 185 is focused by focusing optics 184 and reflects frommirror 182 toward the active area 183 of detector 182. In one aspect,mirror 182 includes a slot through which light emitted from pulsed lightemitting device 181 is passed. Illumination light 186 is emitted frompulsed light emitting device 181, passes through the slot in mirror 182,is collimated by focusing optics 184, and exits the integrated LIDARmeasurement device.

FIGS. 15A-C depict three different light paths through an embodiment 190of an integrated LIDAR measurement device. This embodiment includes apulsed light emitting device 191, a PBS 193, a polarization controlelement 194 (e.g., Pockels cell), a PBS 195, a quarter waveplate 196,mirror element 197 (e.g., a PBS, a half cube with total internalreflection, etc.), delay element 198, polarizing beam combiner 199, halfwaveplate 200, and detector 192. Polarization control element 194 iscoupled to a controller of the integrated LIDAR measurement device. Thecontroller communicates control signal 204 to polarization controlelement 194 that causes the polarization control element to alter thepolarization state of light passing through the polarization controlelement in accordance with control signal 204.

In a first state, depicted in FIG. 15A, polarization control element 194is configured not to change the polarization of light passing throughwhen illumination light 201 is emitted from pulsed light emitting device191. FIG. 15A depicts the path of illumination light 201 throughembodiment 190. Illumination light 201 passes through PBS 193,polarization control element 194, PBS 195, and quarter waveplate 196. Inthe examples depicted in FIGS. 15A-C, the pulsed light emitting device191 emits p-polarized light, and the PBS elements 193 and 194 areconfigured to directly transmit p-polarized light. However, in general,different polarizations may be utilized to achieve the same result.

In a second state, depicted in FIGS. 15B and 15C, polarization controlelement 194 is configured to change the polarization of light passingthrough when return light 202 is detected by detector 192, and light isnot emitted from pulsed light emitting device 191.

FIG. 15B depicts the path of a portion 202A of return light 202 that isp-polarized after passing through quarter waveplate 196. The p-polarizedreturn light passes through PBS 195 and polarization control element194. In this state, polarization control element 194 switches thepolarization of the return light from p-polarization to s-polarization.The s-polarized return light is reflected from PBS 193 toward halfwaveplate 200. Half waveplate 200 switches the polarization again froms-polarization back to p-polarization. polarizing beam combiner 199reflects the p-polarized light toward detector 192.

FIG. 15C depicts the path 202B of the portion of return light 202 thatis s-polarized after passing through quarter waveplate 196. Thes-polarized return light is reflected from beam splitter 195 to mirrorelement 197, through beam delay element 198, through polarizing beamcombiner 199, which directly transmits the s-polarized light ontodetector 192.

Beam delay element 198 is introduced to balance the optical path lengthsof the s and p polarized return light. Beam delay element may be simplya piece of optical glass of appropriate length.

Embodiment 190 also includes a beam path extension element 206 locatedin the illumination beam path between the pulsed light emitting device191 and polarizing beam splitter 193. In some embodiments, beam pathextension element 206 is simply a piece of optical glass of appropriatelength. Beam path extension element 206 is configured to equalize theillumination path length and the length of the return paths 202A and202B. Note that the return path lengths 202A and 202B are equalized bybeam delay element 198. Since the return paths 202A and 202B passthrough additional elements, their effective optical path is longer. Byequalizing the illumination path length with the length of the returnpaths, the return beam is focused to a spot size that approaches thesize of the illumination output aperture. This enables the use of thesmallest sized detector with the least amount of noise and sensitivityto sun noise and highest bandwidth.

Embodiment 190 also includes a beam delay element 205 in return path202B to match the effect of half waveplate 200 in return path 202A.

Due to the finite amount of time required to switch the state of thepolarization control element, the LIDAR based measurement of relativelyshort distances is based on light collected by the return path 202Bdepicted in FIG. 15C. While the polarization control element is changingstate, return light propagating along the path 202A depicted in FIG. 15Bwill not necessarily be subject to a change in polarization. Thus, thislight has a high probability of propagating through PBS 193 to pulsedlight emitting device 191, and thus, will not be detected. Thissituation is acceptable because signal strength is typically not asignificant issue for relatively short range measurements.

However, for relatively long range measurements, after a sufficientperiod of time to ensure that the state of the polarization stateswitching element has changed, return light propagating down both pathsdescribed in FIGS. 15B and 15C is available for detection and distanceestimation.

As discussed hereinbefore, quarter waveplate 196 is desireable. Whenperforming relatively short range measurements, only light passingthough the return path 202B described in FIG. 15C is available. When thepolarization of the return light is completely mixed, half of the lightwill pass through the path described in FIG. 15C. However, when thereturn light has reflected from a specular target, the polarizationremains unchanged. Without introducing the quarter waveplate 196, lightreflected from specular targets would propagate through the pathdescribed in FIG. 15B, and would be undetected or significantly weakenedfor short range measurements when the polarization control element ischanging states.

FIG. 16 depicts an embodiment 220 of an integrated LIDAR measurementdevice that includes an additional polarization control element 221 inreturn path 202B. Embodiment 220 includes like numbered elementsdescribed with reference to embodiment 190. Polarization controlelements 194 and 221 effectively control the amount of return light thatreaches detector 192. As discussed with reference to FIG. 15B, ifpolarization control element 194 does not change the polarization stateof return light 202A, the light is directed to pulsed light emittingdevice 191, not detector 192. Conversely, if polarization controlelement 194 changes the polarization state of return light 202A, thelight is directed to detector 192. Similarly, if polarization controlelement 221 changes the polarization state of return light 202B froms-polarization to p-polarization, the light is directed away fromdetector 192, and ultimately dumped (i.e., absorbed elsewhere).Conversely, if polarization control element 221 does not change thepolarization state of return light 202B, the light is directed towarddetector 192. Since the degree of polarization change imparted bypolarization control elements 194 and 221 is variably controlled (e.g.,Pockels Cells), it follows that the amount of return light that reachesdetector 192 is controlled by a controller of the integrated LIDARmeasurement device (e.g., controller 132) via control signals 204 and222.

For example, as discussed hereinbefore, when performing relatively shortrange measurements, only light passing though the return path 202Bdescribed in FIG. 15C and FIG. 16 is available for detection aspolarizer control element 194 is transitioned from its state depicted inFIG. 15A. During this period of time, there is a risk that detector 192saturates. In this scenario, it is desirable to control polarizationcontrol element 221 such that the polarization of a portion of returnlight 202 is partially changed from s-polarization to p-polarization andthat the p-polarized light component is dumped before it reachesdetector 192.

In general, the timing and profiles of control signals 204 and 222 canbe tuned to maximize the dynamic range of detector 192 for differentenvironmental conditions. For example, previously detected signals,signals from other integrated LIDAR measurement devices, images of thesurrounding environment, or any combination thereof could be utilized toadjust the dynamic range of detector 192 by changing the timing andprofiles of control signals 204 and 222 during operation of anintegrated LIDAR measurement device. In one example, the timing andprofiles of control signals 204 and 222 are programmed as a function ofpulse travel distance. This can be used to avoid detector saturationcaused by objects that are close to the sensor. For larger distancesmeasurement sensitivity is maximized and polarization control element221 is programmed to pass return light 202B without changing itspolarization. In this manner, the maximum amount of return light reachesdetector 192. Multiple profiles could be used depending on illuminationpulse power, features detected in the sensed environment from datacollected in a previous return, etc.

FIG. 17 depicts an embodiment 230 of an integrated LIDAR measurementdevice that includes additional, optional elements that may be addedindividually, or in any combination, to embodiment 190 described withreference to FIGS. 15A-C. Embodiment 230 includes like numbered elementsdescribed with reference to embodiment 190. As depicted in FIG. 17,collimating optics 231 are located in the optical path between pulsedlight emitting device 191 and beam splitter 193. Typically, a pulsedlight emitting device based on laser diode technology or light emittingdiode technology generates a divergent beam of light. By collimating theillumination light emitted from the pulsed light emitting device, asmall beam size is maintained throughout the illumination path. Thisallows the optical elements in the illumination path to remain small.

Also, embodiment 230 includes a focusing lens 232 after quarterwaveplate 196. By refocusing the collomated light transported throughthe integrated LIDAR measurement device, the output aperture of theilluminating device 191 is re-imaged just outside of the integratedLIDAR measurement device, keeping both the crossection of the integratedLIDAR measurement device and the effective exit and entrance aperture ofthe integrated measurement device small. This increases possible pixelpackaging density and pixel resolution. Since focusing lens 232 islocated in the optical path shared by the illumination light and thereturn light, and the illumination and return paths are balanced, animage point 235 is generated at the output of the integrated LIDARmeasurement device. This imaging point 235 is imaged back to both thedetector 192 and the pulsed light emitting device 191. Various opticalelements such as apertures, field stops, pinhole filters, etc. may belocated at image point 235 to shape and filter the images projected ontodetector 192. In addition, embodiment 230 includes a focusing optic 233located in the optical path between the detector 192 and beam combiner199 to focus the return light onto detector 192.

Also, embodiment 190 includes a spectral filter 234 located in thereturn beam path between the focusing optic 233 and beam combiner 199.In some embodiments, spectral filter 234 is a bandpass filter thatpasses light in the spectral band of the illumination beam and absorbslight outside of this spectral band. In many embodiments, spectralfilters operate most effectively when incident light is normal to thesurface of the spectral filter. Thus, ideally, spectral filter 234 islocated in any location in the return beam path where the light iscollimated, or closely collimated.

FIG. 18 depicts a side view of an embodiment 210 of an integrated LIDARmeasurement device including a detector 212, a pulsed light emittingdevice 213 located in front of detector 212 within a lens element 211.FIG. 19 depicts a front view of embodiment 210. As depicted in FIGS.18-19, return light 217 is collected and focused by lens element 211(e.g., a compound parabolic concentrator) onto detector 212. Althoughthe input port 218 of lens element 211 is depicted as planar in FIG. 18,in general, the input port 218 may be shaped to focus return light 217onto detector 212 in any suitable manner. Pulsed light emitting device213 is located within the envelope of lens element 211 (e.g., moldedwithin lens element 211). Although pulsed light emitting device 213blocks a certain amount of return light, its small size relative to thecollection area of lens element 211 mitigates the negative impact.Conductive elements 214 provide electrical connectivity between pulsedlight emitting device 213 and other elements of the integrated LIDARmeasurement device (e.g., illumination driver 133) via conductive leads215. In some embodiments, conductive elements 214 also providestructural support to locate pulsed light emitting device 213 within theenvelope of lens element 211.

FIG. 20 depicts a side view of an embodiment 240 of an integrated LIDARmeasurement device including a detector 242 and a pulsed light emittingdevice 241 located in front of detector 242. As depicted in FIG. 20,return light 246 is collected and focused by focusing optics 244 ontodetector 242. Pulsed light emitting device 241 is located withinfocusing optics 244 (e.g., molded with focusing optics 244). Althoughpulsed light emitting device 241 blocks a certain amount of returnlight, its small size relative to the collection area of focusing optics244 mitigates the negative impact. Conductive elements (not shown)provide electrical connectivity between pulsed light emitting device 241and other elements of the integrated LIDAR measurement device (e.g.,illumination driver 133). In some embodiments, the conductive elementsalso provide structural support to locate pulsed light emitting device241 within focusing optics 244.

FIG. 21 depicts a side view of an embodiment 250 of an integrated LIDARmeasurement device including a detector 253 having an active area 252and a pulsed light emitting device 251 located outside the field of viewof the active area 252 of the detector. As depicted in FIG. 21, aovermold 254 is mounted over the detector. The overmold 254 includes aconical cavity that corresponds with the ray acceptance cone of returnlight 255. In one aspect, illumination light 259 from illuminationsource 251 is injected into the detector reception cone by a fiberwaveguide 257. An optical coupler 256 optically couples illuminationsource 251 (e.g., array of laser diodes) with fiber waveguide 257. Atthe end of the fiber waveguide 257, a mirror element 258 is oriented ata 45 degree angle with respect to the waveguide to inject theillumination light 259 into the cone of return light 255. In oneembodiment, the end faces of fiber waveguide 257 are cut at a 45 degreeangle and the end faces are coated with a highly reflective dielectriccoating to provide a mirror surface. In some embodiments, waveguide 257includes a rectangular shaped glass core and a polymer cladding of lowerindex of refraction. In some embodiments, the entire assembly 250 isencapsulated with a material having an index of refraction that closelymatches the index of refraction of the polymer cladding. In this manner,the waveguide injects the illumination light 259 into the acceptancecone of return light 255 with minimal occlusion.

The placement of the waveguide 257 within the acceptance cone of thereturn light projected onto the active sensing area 252 of detector 253is selected to ensure that the illumination spot and the detector fieldof view have maximum overlap in the far field.

In some embodiments, such as the embodiments described with reference toFIG. 1 and FIG. 2, an array of integrated LIDAR measurement devices ismounted to a rotating frame of the LIDAR device. This rotating framerotates with respect to a base frame of the LIDAR device. However, ingeneral, an array of integrated LIDAR measurement devices may be movablein any suitable manner (e.g., gimbal, pan/tilt, etc.) or fixed withrespect to a base frame of the LIDAR device.

In some other embodiments, each integrated LIDAR measurement deviceincludes a beam directing element (e.g., a scanning mirror, MEMS mirroretc.) that scans the illumination beam generated by the integrated LIDARmeasurement device.

In some other embodiments, two or more integrated LIDAR measurementdevices each emit a beam of illumination light toward a scanning mirrordevice (e.g., MEMS mirror) that reflects the beams into the surroundingenvironment in different directions.

FIG. 22 illustrates a method 300 of performing LIDAR measurements in atleast one novel aspect. Method 300 is suitable for implementation by aLIDAR system such as LIDAR systems 100 illustrated in FIG. 1 and LIDARsystem 10 illustrated in FIG. 2 of the present invention. In one aspect,it is recognized that data processing blocks of method 300 may becarried out via a pre-programmed algorithm executed by one or moreprocessors of controller 132, or any other general purpose computingsystem. It is recognized herein that the particular structural aspectsof LIDAR system 100 do not represent limitations and should beinterpreted as illustrative only.

In block 301, a measurement pulse of illumination light is generated byan illumination source mounted to a printed circuit board.

In block 302, a return pulse of light is detected by a detector mountedto the printed circuit board. The return pulse is an amount of themeasurement pulse reflected from a location in a three dimensionalenvironment illuminated by the corresponding measurement pulse. Themeasurement pulse of illumination light and the return pulse share acommon optical path over a distance within the integrated LIDAR device.

In block 303, an output signal is generated that is indicative of thedetected return pulse.

In block 304, an amount of electrical power is provided to theillumination source by an illumination driver mounted to the printedcircuit board. The provided electrical power causes the illuminationsource to emit the measurement pulse of illumination light.

In block 305, the output signal is amplified by an amount of analogsignal conditioning electronics mounted to the printed circuit board.

In block 306, the amplified output signal is converted to a digitalsignal by an analog to digital converter mounted to the printed circuitboard.

In block 307, a time of flight of the measurement pulse from the LIDARdevice to the measured location in the three dimensional environment andback to the LIDAR device is determined based on the digital signal.

In one or more exemplary embodiments, the functions described may beimplemented in hardware, software, firmware, or any combination thereof.If implemented in software, the functions may be stored on ortransmitted over as one or more instructions or code on acomputer-readable medium. Computer-readable media includes both computerstorage media and communication media including any medium thatfacilitates transfer of a computer program from one place to another. Astorage media may be any available media that can be accessed by ageneral purpose or special purpose computer. By way of example, and notlimitation, such computer-readable media can comprise RAM, ROM, EEPROM,CD-ROM or other optical disk storage, magnetic disk storage or othermagnetic storage devices, or any other medium that can be used to carryor store desired program code means in the form of instructions or datastructures and that can be accessed by a general-purpose orspecial-purpose computer, or a general-purpose or special-purposeprocessor. Also, any connection is properly termed a computer-readablemedium. For example, if the software is transmitted from a website,server, or other remote source using a coaxial cable, fiber optic cable,twisted pair, digital subscriber line (DSL), or wireless technologiessuch as infrared, radio, and microwave, then the coaxial cable, fiberoptic cable, twisted pair, DSL, or wireless technologies such asinfrared, radio, and microwave are included in the definition of medium.Disk and disc, as used herein, includes compact disc (CD), laser disc,optical disc, digital versatile disc (DVD), floppy disk and blu-ray discwhere disks usually reproduce data magnetically, while discs reproducedata optically with lasers. Combinations of the above should also beincluded within the scope of computer-readable media.

Although certain specific embodiments are described above forinstructional purposes, the teachings of this patent document havegeneral applicability and are not limited to the specific embodimentsdescribed above. Accordingly, various modifications, adaptations, andcombinations of various features of the described embodiments can bepracticed without departing from the scope of the invention as set forthin the claims.

What is claimed is:
 1. An integrated light detection and ranging (LIDAR)device, comprising: an illumination source mounted to a printed circuitboard, the illumination source configured to generate a measurementpulse of illumination light; a detector mounted to the printed circuitboard, the detector configured to detect a return pulse of light andgenerate an output signal indicative of the detected return pulse,wherein the return pulse is an amount of the measurement pulse reflectedfrom a location in a three dimensional environment illuminated by thecorresponding measurement pulse, wherein the measurement pulse ofillumination light and the return pulse share a common optical path overa distance within the integrated LIDAR device; an illumination drivermounted to the printed circuit board, the illumination driverelectrically coupled to the illumination source and configured toprovide an amount of electrical power to the illumination source thatcauses the illumination source to emit the measurement pulse ofillumination light; an amount of analog signal conditioning electronicsmounted to the printed circuit board, the analog signal conditioningelectronics configured to amplify the output signal generated by thedetector; an analog to digital converter mounted to the printed circuitboard, the analog to digital converter configured to convert theamplified output signal to a digital signal; and a computing systemconfigured to: receive the digital signal indicative of the detectedamount of light; and determine a time of flight of the measurement pulsefrom the LIDAR device to the measured location in the three dimensionalenvironment and back to the LIDAR device based on the digital signal. 2.The LIDAR device of claim 1, wherein the illumination source and theillumination driver are integrated onto a single Gallium Nitride basedsubstrate that is mounted to the printed circuit board.
 3. The LIDARdevice of claim 1, wherein the return pulse of light and theillumination pulse are separated from the common optical path by a beamsplitter within the LIDAR device.
 4. The LIDAR device of claim 1,wherein the detector includes an active sensing surface area and atransparent aperture within the field of view of the detector.
 5. TheLIDAR device of claim 4, wherein the transparent aperture is a voidthrough the detector.
 6. The LIDAR device of claim 5, wherein theillumination source emits the measurement pulse of illumination lightthrough the transparent aperture in the detector such that themeasurement pulse of illumination light is within the field of view ofthe detector.
 7. The LIDAR device of claim 1, further comprising: anactive optical element having a selectable index of refraction locatedin the common optical path, wherein the active optical element in afirst state directs the return pulse to the detector, and wherein theactive optical element in a second state directs the measurement beam ofillumination light into the common optical path.
 8. The LIDAR device ofclaim 1, further comprising: a first optical element located in thecommon optical path, the first optical element configured to focus thereturn pulse of light onto the detector; a second optical elementlocated in the common optical path, the second optical elementconfigured to direct the measurement beam of illumination light into thecommon optical path, wherein the illumination source is located outsidethe field of view of the detector.
 9. The LIDAR device of claim 1,further comprising: a mirror element located in the common optical path,wherein the mirror element includes a transparent aperture within aportion of the mirror that is within the field of view of the detector,and wherein the illumination source emits the measurement beam ofillumination light through the transparent aperture into the commonoptical path.
 10. The LIDAR device of claim 1, wherein the illuminationsource is located in the shared optical path within a field of view ofthe detector.
 11. The LIDAR device of claim 10, wherein the illuminationsource is embedded in an optical element located in the shared opticalpath within the field of view of the detector.
 12. The LIDAR device ofclaim 1, further comprising: an optical fiber element optically coupledbetween the illumination source located outside a field of view of thedetector and a mirror element located in the common optical path withinthe field of view of the detector.
 13. The LIDAR device of claim 3,further comprising: a first polarization control element located in abeam path of the measurement pulse of illumination light, wherein in afirst state the first polarization control element causes themeasurement pulse of illumination light to pass through the firstpolarization control element, and wherein in a second state the firstpolarization control element causes the return pulse to be reflectedfrom the first polarization control element toward the detector.
 14. TheLIDAR device of claim 13, further comprising: a second polarizationcontrol element located in a beam path of the return pulse, wherein thesecond polarization control element controls an amount of the returnpulse that is directed to the detector.
 15. A method comprising:generating a measurement pulse of illumination light by an illuminationsource mounted to a printed circuit board; detecting a return pulse oflight by a detector mounted to the printed circuit board, wherein thereturn pulse is an amount of the measurement pulse reflected from alocation in a three dimensional environment illuminated by thecorresponding measurement pulse, wherein the measurement pulse ofillumination light and the return pulse share a common optical path overa distance within the integrated LIDAR device; generating an outputsignal indicative of the detected return pulse; providing an amount ofelectrical power to the illumination source by an illumination drivermounted to the printed circuit board that causes the illumination sourceto emit the measurement pulse of illumination light; amplifying theoutput signal by an amount of analog signal conditioning electronicsmounted to the printed circuit board; converting the amplified outputsignal to a digital signal by an analog to digital converter mounted tothe printed circuit board; and determining a time of flight of themeasurement pulse from the LIDAR device to the measured location in thethree dimensional environment and back to the LIDAR device based on thedigital signal.
 16. The method of claim 15, wherein the illuminationsource and the illumination driver are integrated onto a single GalliumNitride based substrate that is mounted to the printed circuit board.17. The method of claim 15, wherein the illumination source emits themeasurement pulse of illumination light through a transparent aperturein an active surface of detector such that the measurement pulse ofillumination light is within the field of view of the detector.
 18. Themethod of claim 15, further comprising: selecting an index of refractionof an active optical element located in the common optical path, whereinthe index of refraction in a first state directs the return pulse to thedetector, and wherein the index of refraction in a second state directsthe measurement beam of illumination light into the common optical path.19. The method of claim 15, further comprising: focusing the returnpulse of light onto the detector with a first optical element located inthe common optical path; directing the measurement beam of illuminationlight into the common optical path with a second optical element locatedin the common optical path, wherein the illumination source is locatedoutside the field of view of the detector.
 20. The method of claim 15,further comprising: emitting the measurement beam of illumination lightthrough a transparent aperture within a portion of a mirror elementwithin a field of view of the detector.
 21. The method of claim 15,wherein the illumination source is located in the shared optical pathwithin a field of view of the detector.
 22. The method of claim 15,further comprising: optically coupling the illumination source locatedoutside a field of view of the detector and a mirror element located inthe common optical path within the field of view of the detector. 23.The method of claim 15, further comprising: selecting a firstpolarization state of a first polarization control element located in abeam path of the measurement pulse of illumination light that causes themeasurement pulse of illumination light to pass through the firstpolarization control element; and selecting a second polarization stateof the first polarization control element that causes the return pulseto be reflected from the first polarization control element toward thedetector.
 24. The method of claim 23, further comprising: selecting apolarization state of a second polarization control element located in abeam path of the return pulse that controls an amount of the returnpulse that is directed to the detector.
 25. An integrated lightdetection and ranging (LIDAR) device, comprising: an illumination sourcemounted to a printed circuit board, the illumination source configuredto generate a measurement pulse of illumination light; a detectormounted to the printed circuit board, the detector configured to detecta return pulse of light and generate an output signal indicative of thedetected return pulse, wherein the return pulse is an amount of themeasurement pulse reflected from a location in a three dimensionalenvironment illuminated by the corresponding measurement pulse, whereinthe measurement pulse of illumination light and the return pulse share acommon optical path over a distance within the integrated LIDAR device;an illumination driver mounted to the printed circuit board, theillumination driver electrically coupled to the illumination source andconfigured to provide an amount of electrical power to the illuminationsource that causes the illumination source to emit the measurement pulseof illumination light; and a computing system configured to determine atime of flight of the measurement pulse from the LIDAR device to themeasured location in the three dimensional environment and back to theLIDAR device based at least in part on output signal.
 26. The LIDARdevice of claim 25, wherein the illumination source and the illuminationdriver are integrated onto a single Gallium Nitride based substrate thatis mounted to the printed circuit board.